Milling Set up question

[Alan Waddington 2Participant @alanwaddington2]

ok, so i just watched a video on FB……not sure it will be viewable on here but this is the link……

**LINK**

Basically boring a set of 4 cylinder barrels on the mill. Not a job iv’e ever tackled, but got me thinking, what would be the easiest method of getting the block correctly lined up square on the table. I reckon i could do it, but it would be a slow and fiddly process. Im guessing there must be a quick and simple method to get set up.?

[Alan Waddington 2Participant @alanwaddington2]

[Mick B1Participant @mickb1]

'Struth.

I'd think that setup's more than a bit flaky, unless there's some support underneath at the back I didn't see. He's clamping on a few mil each end with a long unsupported bit in the middle.

All right as long as he's using light cuts, and nothing whatever goes wrong …

[pgk pgkParticipant @pgkpgk17461]

Don't have to get the cylinder lined up with the table..just adjust with an indicator and x/y axis for each hole..

pgk

[Martin ConnellyParticipant @martinconnelly55370]

This is speculation but could be the way things are done.

The initial machining when new was probably to machine the lower face and to machine the crank bearing pockets. These then become the datums for future machining and so a suitable jig would have the part machined block located on the bearing pockets and machined lower face. The top would then have the face, bolt holes and bores machined. Once sleeves are fitted they can be machined on the same jig. You may also machine other features such as the recess around the slot between the cylinders. Set up then becomes mount the lower face on suitable parallels and align the head so that the recess machining is aligned to the Y axis. You then need to locate the centres of the cylinders as a check of alignment. Do this at the bottom of the cylinder as there will be little or no wear there.

Martin C

[HopperParticipant @hopper]

A lot of motorcycle reboring is done in bike shops by mechanics, not machinists, using a simple boring bar machine. Centring the bore before reboring is often pretty, ahem, basic. Often just basically a tapered fitting on the boring bar that fits into the mouth of the bore while the cylinder is clamped down on the table. The alignment does not have to be perfect. Within a thou or two would be plenty close enough. (There is plenty of side clearance on the gudgeon pin in one direction and almost infinite available variation fore and aft in the direction the crank rotates. Remember, the average engine is not "blueprinted" but relatively roughly put together under production tolerances.)

And, yes set up can be quite flimsy as cuts are small. Usually you are boring to 10 thou bigger than present, so five thou total depth of cut, or a bit less allowing for honing. So possibly done in one cut of four thou depth. Material is nice grade of cast iron so it machines beautifully.

[JasonBModerator @jasonb]

Looking at a few of their other photos and videos they do seem to know what they are doing with engine mods and rebores, that machine has a holder for a Microbore insert so won't be taking big cuts.

[Alan Waddington 2Participant @alanwaddington2]

Posted by pgk pgk on 13/07/2018 11:51:57:

Don't have to get the cylinder lined up with the table..just adjust with an indicator and x/y axis for each hole..

pgk

That’s probably how i would have done it……just seems quite labour intensive swapping the boring head for a clock 4 times and then centereing each hole individually, although i guess most shops doing it for a living would have power drawbars, or perhaps some quick method to attach a clock direct to the boring head ?

I figured there would be an easy way to clock up the block so you could jump between holes using the X axis and a dro for centres.

[Alan Waddington 2Participant @alanwaddington2]

Posted by JasonB on 13/07/2018 12:31:14:

Looking at a few of their other photos and videos they do seem to know what they are doing with engine mods and rebores, that machine has a holder for a Microbore insert so won't be taking big cuts.

Oh they definitely know what they are doing…….highly respected and succesful performance engine building company. I wasn’t questioning their methods or competance……just curious at how the job would be set up, i seem to struggle sometimes with milling setups.

[JasonBModerator @jasonb]

I think you would have to jump back and forth between the two end bores to get them lined up, probably have the clamp a little tighter at one end which you would measure first then tap the other until it matched then back to the first etc. Two big heavy cylindrical squares one in each end bore, a straight edge against then and a dti run along that would get you quiet close.

You would need to know the exact spacing if working along with the DRO but could work that out.

[JasonBModerator @jasonb]

This is how to do it, boring machine with a built in co-ax indicator, start about 60secs in.

[Alan Waddington 2Participant @alanwaddington2]

Posted by JasonB on 13/07/2018 13:17:07:

This is how to do it, boring machine with a built in co-ax indicator, start about 60secs in.

Could have done with a drop of oil on that dti adjuster

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